package main

import (
	"io/ioutil"
	"fmt"
)

func eval(a, b int, op string) int {
	var result int
	switch op {
	case "+":
		result = a + b
	case "-":
		result = a - b
	case "*":
		result = a * b
	case "/":
		result = a / b
	}
	return result
}

func grade(score int) string {
	g := ""
	switch {
	case score <= 100:
		g = "A"
	case score > 100:
		g = "S"
	}
	return g
}

func main() {
	const filename = "abc.txt"
	if contents, err := ioutil.ReadFile(filename); err != nil{
		fmt.Println(err)
	} else {
		fmt.Printf("%s\n", contents)
	}

	fmt.Println(eval(11, 2, "/"))
	fmt.Print(grade(99900))
}